Salmon Fingerlings Research Articles

Expression of muscle-specific genes in atlantic salmon fingerlings (SALMO SALAR L.) in the conditions of aquaculture under the influence of different lighting and feeding regimes

Expression of muscle-specific genes in atlantic salmon fingerlings (SALMO SALAR L.) in the conditions of aquaculture under the influence of different lighting and feeding regimes

Some features of natural spawning and problems of artificial reproduction of the cherry salmon Oncorhynchus masou (Brevoort, 1856)

The article discusses certain aspects of the dispersal and biology of cherry salmon, Oncorhynchus masou (Brevoort, 1856). It is noted that the species is the southernmost within the Pacific Salmon family and is also the only member of the Oncorhynchus genus whose habitat is exclusively in Asia. The decline in the number of cherry salmon across their range has been highlighted, and the main underlying factors have been identified. Some features of cherry salmon spawning run in various parts of their range are examined. A long stay of spawners in fresh water before spawning with preservation of feeding behavior is noted, which makes the species an extremely compelling object of recreational and commercial fishing. Some features of natural reproduction, such as spawning timing and fertility, depending on the habitat and size of the spawners, are indicated. The issue of preserving and restoring the species population is touched upon; the most appropriate method of its implementation is the artificial reproduction of the young with subsequent release into the natural habitat. The paper highlights a number of obstacles to the implementation of such programs, such as the undeveloped technology for growing young masu salmon and the difficulty of optimizing the temperature regime at hatcheries. As one of the limitations to increasing release volumes, it is indicated that masu salmon belongs to a species that have a long freshwater period, with the young spending up to three years in the river. A large number of juvenile masu salmon in the river leads to insufficient food supply and high mortality. In order to overcome this factor, it has been proposed to conduct research aimed at stimulating the smoltification of hatchery salmon fingerlings. This measure will allow significantly increasing the number of smolt and the return rates of spawners, which can be removed without affecting the natural populations.

Detection, sequencing, and tissue distribution of piscine orthoreovirus 2-like virus in diseased coho salmon in Alaska.

We performed a diagnostic disease investigation on a cohort of coho salmon (Oncorhynchus kisutch) fingerlings in Alaska exhibiting anorexia, gaping mouths, anemia, and increased mortality. Histologic examination revealed mild-to-severe myocardial degeneration and lymphohistiocytic and neutrophilic myocarditis, moderate splenic histiocytosis, and mild renal histiocytosis. Piscine orthoreoviruses 1 and 3 were not detected by molecular methods, and no other viruses could be cultured on 3 common diagnostic fish cell lines. De novo assembly produced a viral genome of 10 linear segments with >80% homology to piscine orthoreovirus 2 (PRV2) encoding all 11 PRV2 proteins. An in situ hybridization probe using RNAscope was developed against 697 viral nucleotides identified by sequencing, which revealed viral genome in heart, spleen, gill, kidney, liver, blood, and the lamina propria of the intestines. Our findings are supportive of a novel piscine orthoreovirus most closely related to PRV2 associated with morbidity and mortality of coho salmon in the northeastern Pacific.

Assessment of osmotic adaptation and seawater readiness in juvenile Chinook salmon reared at the Malkinskiy salmon hatchery

Aim: to assessed the readiness of Chinook salmon fingerlings reared at the Malkinskiy salmon hatchery (Kamchatka region) to seawater run and to reverse water-salt transport; to develop a rapid and effective method to determine the readiness of juvenile Chinook salmon to seawater run.Methods: the dynamics of haemoglobin, glucose, haematocrit, blood osmolarity and body weight were studied in juvenile of Chinook salmon of a different sizes exposed in water with salinities of 30 and 40% (experiments in fresh water under the same conditions served as a control, all experiments were carried out in three repetitions).Novelty: a method is described to assess the readiness of juvenile salmonids with a prolonged freshwater period of life to sea water run.Results: the standard “salinity test” does not always reflect the readiness of juveniles to run, and to clarify their physiological state, it is worth studing the dynamics of blood osmolarity during exposure to water with a salinity of 30% (the critical indicator is 340 mOsm l‑1 after a day of experiment). Blood levels of glucose, hemoglobin and hematocrit, as well as the dynamics of body weight are not suitable for assessing salt resistance because off the excessive sensitivity of these indicators. It was shown that juvenile Chinook weighing ≥ 7 g were physiologically ready for run, whereas juveniles weighing ≤ 5 g were not. The intermediate group (5–7 g) exhibited different physiological states in different years.Practical importance: determining the minimum size of fully transformed smolts and finding ways to increase the salt tolerance of juveniles is the way to increase the profitability of the hatchery.

Expression of Muscle-Specific Genes in Aquacultured Atlantic Salmon (Salmo salar L.) Fingerlings under Conditions of Different Lighting and Feeding Regimes

Expression of Muscle-Specific Genes in Aquacultured Atlantic Salmon (Salmo salar L.) Fingerlings under Conditions of Different Lighting and Feeding Regimes

Draft genome sequence of the emerging fish pathogen Flavobacterium tructae strain S12.

The draft genome of Flavobacterium tructae strain S12, isolated from hatchery-reared Chinook salmon (Oncorhynchus tshawytscha) fingerlings, consisted of 5,695,942 bp, a G + C content of 35.6%, 4,775 predicted open reading frames, a putative type IX secretion system, collagenase, and hemolysin. F. tructae strains can be used as models for emerging Flavobacterium pathogens.

Effect of dietary inclusion of microalgae (Nannochloropsis gaditana and Schizochytrium spp) on non-specific immunity and erythrocyte maturity in Atlantic salmon fingerlings.

The parr-smolt transformation in salmonids involves a critical period characterized by systemic changes associated with the fish's immune response. In this context, as a dietary ingredient in functional diets, microalgae offer an alternative due to their nutritional and bioactive compounds that could strengthen the immune status. This study evaluated the effect of a diet supplemented with Schizochytrium spp and Nannochloropsis gaditana on the expression of genes associated with the antibacterial response. Additionally, the study assessed the effect on the leukocyte population and erythrocyte maturity in Salmo salar blood. Fish were fed for 30 days with a microalgal mixture (1:1) at a 10% inclusion. Each diet was randomly assigned to a tank using a completely randomized design (CRD) with four replications. Each tank was stocked with 70 Atlantic salmon fingerlings with an initial mean weight of 78.87±0.84. Transcription levels were quantified and analyzed by qRT-PCR from cell isolates and mucus tissue. Furthermore, cell count and identification of leukocytes and classification of cellular maturity of erythrocytes using a neural network with a multilayer perceptron (MLP) were performed. Our results showed a significant (p<0.05) increase in fold change expression of C3 (2.54±0.65) and NK-Lysine (6.84±0.94) in erythrocytes of microalgae-supplemented fish. Moreover, a significant increase of 1.59 and 2.35 times in monocytes and immature erythrocytes, respectively, was observed in the same group of fish (p<0.05). This study's results indicate that dual microalgae (Schizochytrium spp and N. gaditana) supplementation can increase innate humoral antibacterial components, particularly in erythrocyte tissue, and increase phagocytic cells and immature erythrocytes in S. salar blood.

Phospholipid Composition of Fingerlings of Atlantic Salmon Salmo salar during Growth and Development in Aquaculture: The Effect of Different Lighting and Feeding Regimes.

The effect of different feeding and lighting regimes (natural and continuous) on the phospholipid composition of Atlantic salmon fingerlings reared in commercial aquaculture in the summer-autumn period in North Ossetia-Alania was studied. Qualitative and quantitative determination of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, lysophosphatidylcholine, sphingomyelin was performed by high-performance liquid chromatography. A decrease (September-November) in the content of the studied phospholipids in fingerlings decreased, which should be considered primarily as a biochemical adaptation of development and preparation of juveniles for the upcoming smoltification. The effects of lighting and feeding regime on phospholipid composition were found mainly in the fish reared under constant lighting and 24/7 feeding and the fish reared under natural light and feeding during daylight hours. However, the observed changes were not specific to a particular experimental group of fish in the framework of this study.

The Influence of Different Lighting and Feeding Regimes on the Activity of Metabolic Enzymes in Farmed Atlantic Salmon Fingerlings

The Influence of Different Lighting and Feeding Regimes on the Activity of Metabolic Enzymes in Farmed Atlantic Salmon Fingerlings

The Influence of Different Lighting and Feeding Regime on the Activity of Energy Metabolism Enzymes in Farmed Atlantic Salmon Fingerlings

The effect of constant and natural lighting modes in combination with different feeding regimes on the activity of energy and carbohydrate metabolism enzymes in the muscles and liver of salmon under-yearlings artificially grown in aquaculture in the southern region of Russia was investigated. The revealed differences in the activity of the studied enzymes in under-yearlings indicate changes in the level of energy metabolism and the use of carbohydrates in the processes of ATP synthesis and other biosynthesis pathways in muscles and liver, depending on lighting conditions and in combination with the feeding regime. The high level of aerobic metabolism in the muscles and the increased use of carbohydrates in glycolysis in the liver in salmon fingerlings raised under constant light corresponded to their highest average weight gain. In individuals from all experimental groups, changes in the activity of the studied enzymes were found in dependence on the time after the start of the experiment, that indicated an increase in the levels of aerobic and anaerobic metabolism in muscles and glycolysis in the liver, necessary for the biosynthesis processes during growth.

PHOSPHOLIPID COMPOSITION OF FINGERLINGS OF ATLANTIC SALMON &lt;i&gt;SALMO SALAR&lt;/i&gt; DURING GROWTH AND DEVELOPMENT IN AQUACULTURE: THE EFFECT OF DIFFERENT LIGHTING AND FEEDING REGIMES

The effect of different modes of feeding and lighting (natural and continuous) on the phospholipid composition of Atlantic salmon fingerlings reared under commercial aquaculture in the summer-autumn period in North Ossetia-Alania was studied. Qualitative and quantitative determination of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, lysophosphatidylcholine, sphingomyelin was carried out by high performance liquid chromatography. A decrease (September-November) The content of the studied phospholipids in fingerlings decreased, which should be considered primarily as a biochemical adaptation of development, preparation of juveniles for the upcoming smoltification. The effects of lighting and feeding regime on phospholipid composition were found mainly in fish reared under constant lighting and 24/7 feeding and fish reared under natural light and feeding during daylight hours, however, the observed changes were not specific to a particular experimental group of fish in the framework of this study.

Parameters of Lipid Metabolism in Underyearlings of Atlantic Salmon &lt;i&gt;Salmo salar&lt;/i&gt; Reared under Different Regimes of Photoperiod and Feeding Modes in Aquaculture in the Sourthern Region of Russia

A comparative study of the lipid and fatty acid composition of Atlantic salmon underyearlings reared under natural and continuous light in commercial aquaculture in the summer-autumn period in North Ossetia-Alania was carried out. A stable change in the main indicators of lipid metabolism in salmon underyearlings from September to November was found, aimed at preparing juveniles for smoltification. A change in key fatty acid indicators was detected: an increase in the content of PUFAs due to (n-3) PUFAs, and the “marine” type of PUFA – 22:6 (n-3), high values of the ratios (n-3)(n-6) PUFA, 18:3(n-3)/18:2 (n-6), 22:6(n-3)/ 18:3(n-3). It has been shown the stimulating effect of the combined and stable action of the continuous photoperiod and feeding in the summer-autumn period on the preparation for smoltification of Atlantic salmon fingerlings grown under aquaculture conditions.

Feeding and food supply of salmons in the Okhotsk Sea in autumn of 2018-2019

In the autumn months of 2018-2019, food spectra of salmons were quite diverse in the Okhotsk Sea. Amphipods prevailed in the diet of juvenile pink and chum salmon that corresponded to these zooplankton species abundance in the southern part of the sea; other significant portions of their diet were presented by euphausiids, copepods, arrowworms, pteropods, and oikopleura. Decapods, fish and squids were in the diet of masu, coho and chinook salmon. Portion of zooplankton was about 100 % in the diet of pink salmon fingerlings, but only 98 % in the diet of chum salmon fingerlings with 2 % portion of squids. Grazing by salmons was insignificant: 0.2-0.3 % of the total zooplankton biomass within the periods of observation (18 days in 2018 and 13 days in 2019), or 0.04-2.0 % for certain taxonomic groups, except of pteropods and oikopleura with the consumed portions of 4-7 % and 7-12 %, respectively. However, the daily consumption by salmons relative to daily production of some groups was significant in October, 2018 and reached 97 % for amphipods and &gt; 200 % for euphausiids in the northeastern Okhotsk Sea (biostatistical areas 6-8) and 48 and 27 %, respectively, in the entire surveyed area. This ratio was twice lower in October, 2019, as 24 % for amphipods and 12 % for euphausiids. Daily consumption of copepods and arrowworms never exceeded 2 % of their daily production. The most favorable conditions for nekton feeding in fall of both years were observed in the northwestern Okhotsk Sea, and the worst conditions — in its northeastern part, with moderate conditions without deficit of prey in the central part (biostatistical area 9) and southern part (biostatistical areas 12, 13), where the biomass of forage plankton exceeded the biomass of nekton in 30-97 times in 2018 and in 56-76 times in 2019.

Mycobacterium salmoniphilum and M. chelonae in Captive Populations of Chinook Salmon.

Chinook Salmon Oncorhynchus tshawytscha is a keystone fish species in the Pacific Northwest. In 2019, unusual mortalities occurred in two different populations of cultured fingerlings from the same facility in California, USA. The systems consist of outdoor, enclosed, flow-through freshwater tanks that are maintained at 18±1°C. Clinical signs and gross findings were only observed in one population and included abnormal swimming, inappetence, lethargy, skin discoloration, and the presence of multifocal nodular and ulcerative skin lesions. Microscopic lesions were infrequent and consisted of severe, locally extensive granulomatous dermatitis and myositis and mild, multifocal, granulomatous branchitis, myocarditis, and hepatitis. Intracellular acid-fast organisms were observed within areas of granulomatous myositis. Posterior kidney swabs were collected and inoculated in nutrient-rich and selective agar media and incubated at 25°C for 2weeks. Visibly pure bacterial colonies were observed 7-10 d postinoculation. Partial sequences of 16S rRNA initially identified the recovered bacteria as members of the genus Mycobacterium. However, marked variability was observed among Mycobacterium spp. isolates by using repetitive extragenic palindromic polymerase chain reaction fingerprinting. Amplification and sequencing of the ribosomal RNA internal transcribed spacer, 65-kDa heat shock protein, and RNA polymerase β-subunit gene of the cultured isolates identified M. salmoniphilum and M. chelonae, discrete members of the M. chelonae-abscessus complex, isolated from diseased Chinook Salmon fingerlings.

Host-specific preference of some Flavobacterium psychrophilum multilocus sequence typing genotypes determines their ability to cause bacterial coldwater disease in coho salmon (Oncorhynchus kisutch).

Flavobacterium psychrophilum causes bacterial coldwater disease (BCWD) in salmonids, resulting in significant losses worldwide. Several serotyping and genetic studies of F.psychrophilum have suggested some geno-/serotypes may be either host-specific or generalistic in nature; however, this association has not been adequately explored in vivo using more natural exposure routes. Herein, F.psychrophilum isolate US19-COS, originally recovered from coho salmon (Oncorhynchus kisutch) and belonging to multilocus sequence typing clonal complex (CC) CC-ST9, and isolate US53-RBT, recovered from rainbow trout (Oncorhynchus mykiss) and belonging to CC-ST10, were serotyped via PCR, evaluated for proteolytic activity and utilized to determine their median lethal dose in immersion-challenged coho salmon fingerlings. US19-COS belonged to serotype 0, hydrolysed casein and gelatin but not elastin, led to fulminant multiorgan infections and elicited severe gross and microscopic pathology. In contrast, US53-RBT, belonging to serotype 2, hydrolysed all three substrates, but did not lead to detectable infections, disease signs or mortality in any exposed coho salmon despite proving virulent to rainbow trout in previous experiments. This study provides in vivo evidence for potential host specificity of some F. psychrophilum genotypes that can also be serologically distinct, a matter of importance towards better understanding F. psychrophilum disease ecology and epidemiology.

Feeding Whole Thraustochytrid Biomass to Cultured Atlantic Salmon (Salmo salar) Fingerlings: Culture Performance and Fatty Acid Incorporation

Replacement of fish oil by 5% thraustochytrid whole cell biomass in diets for Atlantic salmon had no ill effect on fish growth performance, carcass total lipid and total fatty acid content. Carcass fatty acid composition indicated incorporation of the dietary thraustochytrid-derived fatty acids. This was confirmed by compound specific stable isotope analysis (CSIA) which revealed significantly 13C-depleted (δ13C value of −24‰) ω3 long-chain (≥C20) polyunsaturated fatty acids (ω3 LC-PUFAs) in the fingerlings fed the thraustochytrid biomass containing diet, reflecting the highly 13C-depleted glycerol used to grow the thraustochytrid cultures. This finding demonstrates the bioavailability of the ω3 LC-PUFA of the Australian strain thraustochytrid culture (TC) 20 from the whole cell biomass that was partly cultivated on crude glycerol produced during biodiesel manufacturing. This paper demonstrates the value of Australian thraustochytrid strains grown heterotrophically for their wider biotechnological potential including as a source of higher value lipids, in particular the health-benefitting ω3 LC-PUFA, for use in aquaculture and other applications.

N-3 Canola oil effectively replaces fish oil as a new safe dietary source of DHA in feed for juvenile Atlantic salmon.

Limited availability of fish oils (FO), rich in n-3 long-chain (≥C20) PUFA, is a major constraint for further growth of the aquaculture industry. Long-chain n-3 rich oils from crops GM with algal genes are promising new sources for the industry. This project studied the use of a newly developed n-3 canola oil (DHA-CA) in diets of Atlantic salmon fingerlings in freshwater. The DHA-CA oil has high proportions of the n-3 fatty acids (FA) 18 : 3n-3 and DHA and lower proportions of n-6 FA than conventional plant oils. Levels of phytosterols, vitamin E and minerals in the DHA-CA were within the natural variation of commercial canola oils. Pesticides, mycotoxins, polyaromatic hydrocarbons and heavy metals were below lowest qualifiable concentration. Two feeding trials were conducted to evaluate effects of two dietary levels of DHA-CA compared with two dietary levels of FO at two water temperatures. Fish increased their weight approximately 20-fold at 16°C and 12-fold at 12°C during the experimental periods, with equal growth in salmon fed the FO diets compared with DHA-CA diets. Salmon fed DHA-CA diets had approximately the same EPA+DHA content in whole body as salmon fed FO diets. Gene expression, lipid composition and oxidative stress-related enzyme activities showed only minor differences between the dietary groups, and the effects were mostly a result of dietary oil level, rather than the oil source. The results demonstrated that DHA-CA is a safe and effective replacement for FO in diets of Atlantic salmon during the sensitive fingerling life-stage.

The Effects of a Synbiotic Mixture of Galacto-Oligosaccharides and Bacillus Strains in Caspian Salmon, Salmo trutta caspius Fingerlings.

The effect of dietary supplementation with a synbiotic mixture of galacto-oligosaccharides (GOS) and Bacillus spp. was examined in Caspian salmon, Salmo trutta caspius (Kessler, 1877) fingerlings. Caspian salmon fed with the synbiotic diet had significantly higher weight gain rate, protein efficiency ratio, and survival rate, as well as lower feed conversion ratio, compared to the control group (P < 0.05). The serum protein, albumin, globulin, and lactate dehydrogenase levels of the fish fed with the synbiotic diet were significantly higher than the control group (P < 0.05), while the serum alkaline phosphatase levels were significantly lower (P < 0.05). The activities of the innate immune response parameters, including lysozyme, superoxide dismutase, and catalase were significantly higher in the Caspian salmon fed with the synbiotic diet (P < 0.05). The gut microbiota of the Caspian salmon fed with the synbiotic diet contained significantly elevated total viable aerobic bacterial counts (TVABCs), lactic acid bacteria (LAB) levels, and LAB/TVABCs ratio (P < 0.05). Additionally, the gut activities of amylase, trypsin, and chymotrypsin in the gut, as well as the trypsin/chymotrypsin ratio, were significantly increased in the fish that received the synbiotic diet (P < 0.05). In conclusion, the combined GOS and Bacillus spp. supplement positively affected the growth, survival rate, immunobiochemical parameters, digestive activity, and beneficial microbial density in the gut of Caspian salmon fingerlings.

A systemic study of lipid metabolism regulation in salmon fingerlings and early juveniles fed plant oil.

In salmon farming, the scarcity of fish oil has driven a shift towards the use of plant-based oil from vegetable or seed, leading to fish feed low in long-chain PUFA (LC-PUFA) and cholesterol. Atlantic salmon has the capacity to synthesise both LC-PUFA and cholesterol, but little is known about the regulation of synthesis and how it varies throughout salmon life span. Here, we present a systemic view of lipid metabolism pathways based on lipid analyses and transcriptomic data from salmon fed contrasting diets of plant or fish oil from first feeding. We analysed four tissues (stomach, pyloric caeca, hindgut and liver) at three life stages (initial feeding 0·16 g, 2·5 g fingerlings and 10 g juveniles). The strongest response to diets higher in plant oil was seen in pyloric caeca of fingerlings, with up-regulation of thirty genes in pathways for cholesterol uptake, transport and biosynthesis. In juveniles, only eleven genes showed differential expression in pyloric caeca. This indicates a higher requirement of dietary cholesterol in fingerlings, which could result in a more sensitive response to plant oil. The LC-PUFA elongation and desaturation pathway was down-regulated in pyloric caeca, probably regulated by srebp1 genes. In liver, cholesterol metabolism and elongation and desaturation genes were both higher on plant oil. Stomach and hindgut were not notably affected by dietary treatment. Plant oil also had a higher impact on fatty acid composition of fingerlings compared with juveniles, suggesting that fingerlings have less metabolic regulatory control when primed with plant oil diet compared with juveniles.

The Emerging Fish Pathogen Flavobacterium spartansii Isolated from Chinook Salmon: Comparative Genome Analysis and Molecular Manipulation.

Flavobacterium spartansii strain T16T was isolated from a disease outbreak in hatchery-reared Chinook salmon (Oncorhynchus tshawytscha) fingerlings. To gain insight into its genomic content, structure and virulence pathogenesis factors, comparative genome analyses were performed using genomes from environmental and virulent Flavobacterium strains. F. spartansii shared low average nucleotide identity (ANI) to well-known fish-pathogenic flavobacteria (e.g., F. columnare, F. psychrophilum, and F. branchiophilum), indicating that it is a new and emerging fish pathogen. The genome in T16T had a length of 5,359,952 bp, a GC-content 35.7%, and 4,422 predicted protein-coding sequences. Flavobacterium core genome analysis showed that the number of shared genes decreased with the addition of input genomes and converged at 1182 genes. At least 8 genomic islands and 5 prophages were predicted in T16T. At least 133 virulence factors associated with virulence in pathogenic bacteria were highly conserved in F. spartansii T16T. Furthermore, genes linked to virulence in other bacterial species (e.g., those encoding for a type IX secretion system, collagenase and hemolysin) were found in the genome of F. spartansii T16T and were conserved in most of the analyzed pathogenic Flavobacterium. F. spartansii was resistant to ampicillin and penicillin, consistent with the presence of multiple genes encoding diverse lactamases and the penicillin-binding protein in the genome. To allow for future investigations into F. spartansii virulence in vivo, a transposon-based random mutagenesis strategy was attempted in F. spartansii T16T using pHimarEm1. Four putative gliding motility deficient mutants were obtained and the insertion sites of pHimarEm1 in the genome of these mutants were characterized. In total, study results clarify some of the mechanisms by which emerging flavobacterial fish pathogens may cause disease and also provide direly needed tools to investigate their pathogenesis.